Preparation method of octagonal radio frequency quadrupole field cavity electrode

Abstract

The invention provides a preparation method of an octagonal radio frequency quadrupole field cavity electrode, and relates to the technical field of medical accelerators. The preparation method comprises the following steps: performing finish machining on one side of each electrode material according to a rough reference surface of each electrode material so as to determine an initial positioning surface and an initial modulation line of each electrode material; the actual position relation between the initial modulation line of each electrode material and the initial positioning face of each electrode material is determined, finish machining is carried out, and a target modulation line and a target welding face of each electrode material after finish machining are obtained; and according to the target modulation line and the target welding surface of each fine-machined electrode material, the multiple fine-machined electrode materials are welded, and the octagonal radio frequency quadrupole field cavity electrode is obtained.

Description

Technical Field

[0001] This disclosure relates to the field of medical accelerator technology, and in particular to a method for fabricating an octagonal radio frequency quadrupole cavity electrode. Background Technology

[0002] The octagonal radio frequency quadrupole cavity is a key component of particle accelerators, and its performance directly depends on the precision of the cavity assembly formed by the internal electrode materials. The special wavy profile (modulation line) of the inner surface of the electrode is crucial for generating the required accelerating and focusing electric field. It requires not only micrometer-level profile tolerances but also extremely precise relative positioning with the external mounting reference surface. Existing fabrication techniques typically face severe challenges: First, during multiple machining and heat treatment processes, the release of residual stress inside the electrode can easily lead to unpredictable deformation, compromising the already achieved machining precision. Second, in traditional sequential machining methods, positioning reference errors inevitably accumulate and propagate to critical functional surfaces, causing inaccurate alignment of the peaks and troughs of adjacent electrodes during final assembly. Furthermore, the lack of online compensation methods for systematic errors such as machine tool thermal deformation makes it difficult to guarantee the stability of machining accuracy. These factors make it difficult to meet design requirements for key performance parameters such as cavity field flatness, symmetry, and resonant frequency, hindering the reliable manufacturing and industrial application of high-performance accelerators. Summary of the Invention

[0003] In view of the above problems, embodiments of this disclosure provide a method for fabricating an octagonal radio frequency quadrupole cavity electrode, comprising: acquiring a plurality of electrode materials and pre-processing the plurality of electrode materials to form a coarse reference surface on each of the plurality of electrode materials; performing finishing on one side of each electrode material according to the coarse reference surface of each electrode material to determine the initial positioning surface of each electrode material; determining the initial modulation line of each electrode material according to the initial positioning surface of each electrode material; determining the actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material, and performing finishing on each electrode material according to the actual positional relationship to obtain a plurality of finished electrode materials; determining the target positioning surface and the target welding surface of each finished electrode material according to the plurality of finished electrode materials; determining the target modulation line of each finished electrode material according to the target positioning surface, and welding the plurality of finished electrode materials according to the target modulation line and the target welding surface of each finished electrode material to obtain an octagonal radio frequency quadrupole cavity electrode.

[0004] According to embodiments of this disclosure, the plurality of electrode materials include: a horizontal electrode material and a vertical electrode material, wherein the horizontal electrode material is a W-shaped electrode material and the vertical electrode material is a T-shaped electrode material.

[0005] According to embodiments of this disclosure, finishing is performed on one side of each electrode material based on a rough reference surface of each electrode material, including: placing the horizontal electrode material on a prefabricated machining fixture, the machining fixture including a support block and a tightening screw; adjusting the support block by the tightening screw to fix the horizontal electrode material; and finishing is performed on one side of the fixed horizontal electrode material.

[0006] According to embodiments of this disclosure, before finishing one side of each electrode material based on a rough reference surface of each electrode material, the method further includes: performing stress-relief annealing on each electrode material.

[0007] According to embodiments of this disclosure, stress-relief annealing of each electrode material includes: heating the electrode material at 300°C-350°C for 4 hours and holding it at that temperature for 2 hours; cooling the electrode material after holding it at that temperature for 2 hours to 60°C and then air-cooling it.

[0008] According to embodiments of this disclosure, determining the actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material includes: determining the dimensional positional tolerance between the initial modulation line of each electrode material and the initial positioning surface of each electrode material; determining the thermal deformation law of the electrode material based on the dimensional positional tolerance; and determining the actual positional relationship based on the thermal deformation law.

[0009] According to an embodiment of this disclosure, a solder groove is provided on the target welding surface of the electrode material, and welding multiple electrode materials includes: filling solder into the solder groove of each electrode material; and welding multiple electrode materials according to the target modulation line, target welding surface and solder groove of each electrode material.

[0010] According to embodiments of this disclosure, before welding multiple finely processed electrode materials, the method further includes: placing the multiple finely processed electrode materials in a constant temperature environment for a preset time; and performing quality inspection on the multiple finely processed electrode materials after the preset time of placement.

[0011] According to embodiments of this disclosure, before welding multiple finished electrode materials, the method further includes: sequentially performing chemical cleaning, water rinsing, and alcohol dehydration operations on each of the multiple finished electrode materials.

[0012] According to embodiments of this disclosure, pretreatment of multiple electrode materials includes removing the original oxide layer and stress layer from the surfaces of the multiple electrode materials.

[0013] The method disclosed herein determines the initial electrical positioning surface by using a coarse reference surface of the electrode material, and determines the actual positional relationship between the initial modulation line and the initial modulation line by using the initial positioning surface. Then, it feeds back the actual positional relationship to process the electrode material, thereby achieving precise positioning of the target positioning surface and the target modulation line, reducing errors caused by thermal equilibrium, and ensuring the stability of product quality. Attached Figure Description

[0014] The foregoing contents, as well as other objects, features, and advantages of this disclosure, will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0015] Figure 1 A flowchart illustrating a method for fabricating an octagonal radio frequency quadrupole field cavity electrode according to an embodiment of the present disclosure is shown schematically.

[0016] Figure 2 A schematic diagram illustrating the structure of an octagonal radio frequency quadrupole field cavity electrode according to an embodiment of the present disclosure is shown.

[0017] Figure 3 A schematic diagram of the structure of a horizontal electrode material according to an embodiment of the present disclosure is shown.

[0018] Figure 4 A schematic diagram of the machining tooling according to an embodiment of the present disclosure is shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this disclosure clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0020] It should be noted that similar or identical parts are referred to by the same reference numerals in the accompanying drawings or description. The technical features of the various embodiments exemplified in the specification can be freely combined to form new solutions without conflict. Furthermore, each claim can stand alone as an embodiment, or the technical features in the various claims can be combined to form new embodiments. In the drawings, the shape or thickness of the embodiments may be enlarged and indicated in a simplified or convenient manner. Moreover, elements or implementations not shown or described in the drawings are those known to those skilled in the art. Additionally, although this document provides examples of parameters containing specific values, it should be understood that the parameters need not be exactly equal to the corresponding values, but can approximate the corresponding values ​​within acceptable error tolerances or design constraints.

[0021] Unless there are technical obstacles or contradictions, the various embodiments described above in this disclosure can be freely combined to form other embodiments, all of which are within the protection scope of this disclosure.

[0022] Although this disclosure has been described in conjunction with the accompanying drawings, the embodiments disclosed in the drawings are intended to illustrate preferred embodiments of this disclosure and should not be construed as limiting the disclosure. The dimensions in the drawings are merely illustrative and should not be construed as limiting the disclosure.

[0023] While some embodiments of the general concept of this disclosure have been shown and described, those skilled in the art will understand that changes may be made to these embodiments without departing from the principles and spirit of the general concept of this disclosure, the scope of which is defined by the claims and their equivalents.

[0024] Figure 1 A flowchart illustrating a method for fabricating an octagonal radio frequency quadrupole field cavity electrode according to an embodiment of the present disclosure is shown.

[0025] like Figure 1 As shown, embodiments of this disclosure provide a method for fabricating an octagonal radio frequency quadrupole field cavity electrode, including operations S110~S160.

[0026] In operation S110, multiple electrode materials are acquired and preprocessed to form a coarse reference surface on each of the multiple electrode materials.

[0027] In some embodiments, electrode material refers to the metallic raw material used to manufacture the electrode, such as rectangular oxygen-free copper material. A rough reference surface refers to a surface with a certain degree of flatness and orientation formed through preliminary processing. Its accuracy requirements are not high; it is mainly used to provide an initial, stable positioning and measurement reference for subsequent processing steps.

[0028] First, ultrasonic non-destructive testing can be performed on the electrode material to detect any internal defects such as cracks or impurities that may affect the performance of the final part. Then, the electrode material is sawn to cut it into blanks according to its final contour shape, reducing the amount of material removed and material wastage in subsequent machining. Next, these pre-formed blanks are pre-milled on a machine tool to remove the original oxide layer and stress layer from multiple electrode material surfaces.

[0029] These machined planes constitute the rough reference planes. Although they have relatively rough surfaces and large dimensional tolerances, they establish the initial geometric orientation of the workpiece, enabling the workpiece to be reliably clamped on the machine tool and serving as the starting point for dimensional measurements in all subsequent machining processes.

[0030] Figure 2 A schematic diagram of an octagonal radio frequency quadrupole field cavity electrode according to an embodiment of the present disclosure is shown. Figure 3 A schematic diagram of the structure of a horizontal electrode material according to an embodiment of the present disclosure is shown.

[0031] In some embodiments, such as Figure 2 As shown, according to an embodiment of this disclosure, the plurality of electrode materials includes: two horizontal electrode materials 1 and two vertical electrode materials 2, wherein the horizontal electrode materials 1 are W-shaped electrode materials and the vertical electrode materials 2 are T-shaped electrode materials. Different processing methods can be used depending on the desired shape of the electrode materials. For example, when the electrode material is a vertical electrode material 2, its mutually perpendicular side surfaces and bottom surfaces can be processed; when the electrode material is a horizontal electrode material 1, its bottom surface and one side surface can be processed.

[0032] The structure of the horizontal electrode material 1 is as follows: Figure 3 As shown, the horizontal electrode material 1 has three protruding wings, which together form a W shape. The W-shaped electrode material is prone to elastic deformation and vibration under the action of cutting force, and the stress state of the W-shaped electrode material is complex. If it cannot be clamped securely, it is very easy to generate microcracks or deformation during heat treatment.

[0033] In operation S120, based on the rough reference surface of each electrode material, a finishing process is performed on one side of each electrode material to determine the initial positioning surface of each electrode material.

[0034] In some embodiments, one side of each electrode material can refer to the back side of the electrode, i.e., the side opposite to the inner cavity surface that ultimately forms the beam channel. The initial positioning surface is a plane formed on the basis of a coarse reference through higher precision machining, with a precision significantly higher than that of the coarse reference surface, for more accurate electrode positioning.

[0035] After establishing the rough datum surface, precision machining tools can be used to cut specific areas on the back of the electrode material. This process requires several steps: first, the back surface is semi-finished to approximate its final shape, leaving a small, uniform machining allowance. Then, critical areas for mounting and welding are milled or ground with higher precision. These finished surfaces are the initial locating surfaces, typically including mounting surfaces for the electrode to mate with the support structure, and mating surfaces for welding with other parts. After machining, measuring instruments can be used to check the flatness, parallelism, and perpendicularity of these surfaces to ensure they meet process requirements.

[0036] Figure 4 A schematic diagram of the machining tooling according to an embodiment of the present disclosure is shown.

[0037] like Figure 4As shown, according to an embodiment of the present disclosure, fine machining is performed on one side of each electrode material based on a rough reference surface of each electrode material, including: placing the horizontal electrode material 1 on a prefabricated machining fixture, the machining fixture including a support block and a tightening screw; adjusting the support block by the tightening screw to fix the horizontal electrode material 1; and performing fine machining on one side of the fixed horizontal electrode material 1.

[0038] The embodiments of this disclosure design a special machining fixture for W-shaped horizontal electrode materials to ensure the machining accuracy of the precision machining process of horizontal electrode materials and improve the stability of electrode machining quality.

[0039] In operation S130, the initial modulation line of each electrode material is determined based on the initial positioning surface of each electrode material.

[0040] In some embodiments, the electrode material can be flipped so that its pre-machined initial positioning surface faces the machine tool table, ensuring that the initial positioning surface is parallel to the machine tool table plane. Using the initial positioning surface as the reference origin for tool setting and programming, a diamond-insert ball end mill can be used to mill the inner cavity surface of the electrode according to a preset digital model trajectory. This machining aims to shape the basic wave shape of the modulation line, but a uniform thickness allowance (e.g., 0.3 mm) is intentionally retained across the entire inner cavity surface; therefore, the resulting profile is called the initial modulation line. The machining process needs to be performed in a constant temperature environment, and the machine tool should be preheated to a thermally stable state to minimize the impact of thermal deformation on shape accuracy.

[0041] In operation S140, the actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material is determined, and each electrode material is finely processed according to the actual positional relationship to obtain multiple finely processed electrode materials.

[0042] According to embodiments of this disclosure, determining the actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material includes: determining the dimensional positional tolerance between the initial modulation line of each electrode material and the initial positioning surface of each electrode material; determining the thermal deformation law of the electrode material based on the dimensional positional tolerance; and determining the actual positional relationship based on the thermal deformation law.

[0043] In some embodiments, after the initial modulation line machining is completed, a machine tool probe can be used to perform high-density sampling measurements on the initial modulation line contour and the initial positioning surface to obtain a large number of three-dimensional coordinate data points. The dimensional and positional deviations between the two in multiple directions are then calculated, i.e., dimensional and positional tolerances. Subsequently, without changing the workpiece clamping, and while maintaining continuous machine tool operation, the same feature surfaces are measured again at intervals. By repeating this cycle multiple times, the sequence of tolerance data obtained from each measurement over time or temperature is recorded. Analyzing this data sequence allows for the summarization of the direction and approximate magnitude of the workpiece's dimensional expansion or contraction due to heat under the current specific machining parameters and environment, i.e., the thermal deformation law. Finally, the initially measured static dimensional and positional tolerances are vector-superimposed with the predicted thermal deformation that may occur during the subsequent finishing stage, thereby calculating the spatial relationship between the initial modulation line and the initial positioning surface on the workpiece at the planned finishing time. This is the corrected actual positional relationship used to generate the final finishing path.

[0044] Subsequently, using the measured actual position of the initial modulation line as a new reference, the initial positioning surface on the back is subjected to final finishing, removing any remaining machining allowance to achieve the final dimensions and accuracy specified in the drawing. Next, using the already machined final positioning surface as a precise reference, the machining program is run again to completely remove the uniform allowance reserved on the initial modulation line, thus obtaining a modulation line with the required contour accuracy. After this step, both the inner cavity modulation line and the back positioning surface of the octagonal RF quadrupole field cavity electrode achieve the required finishing dimensions.

[0045] The method in this embodiment first measures the actual spatial position of the initial modulation line, then refines the initial positioning surface in reverse based on this, and finally completes the final machining of the modulation line using the corrected final positioning surface as a reference. This process actively offsets the cumulative effects of machine tool positioning errors, clamping deviations, and tool setting errors, reduces errors caused by machine tool thermal balance, ensures product quality stability, and improves production efficiency.

[0046] According to embodiments of this disclosure, each electrode material may also undergo stress-relief annealing before finishing one side of each electrode material, based on a rough reference surface of each electrode material.

[0047] The stress-relief annealing process for each electrode material includes: heating the electrode material at 300℃-350℃ for 4 hours and holding it at that temperature for 2 hours; then cooling the electrode material after holding it at that temperature to 60℃ and air cooling it.

[0048] By employing a precisely controlled low-temperature annealing process, the internal residual stress accumulated in the electrode material during the initial casting, forging, and rough machining processes can be reduced or eliminated. If left untreated, this stress can lead to unpredictable deformation of the workpiece during subsequent finishing stages or long-term use, thereby compromising the achieved machining accuracy. Specific heating and holding parameters (300℃-350℃, 4 hours of heating followed by 2 hours of holding) are designed to allow for a sufficient recovery process within the material, promoting lattice reconstruction to relax stress while preventing recrystallization or material softening. Controlling the cooling rate to 60℃ followed by air cooling prevents the introduction of new thermal stress due to excessively rapid cooling.

[0049] In operation S150, the target positioning surface and target welding surface of each finished electrode material are determined based on multiple finished electrode materials.

[0050] In operation S160, the target modulation line of each finely machined electrode material is determined according to the target positioning surface, and multiple finely machined electrode materials are welded according to the target modulation line and target welding surface of each finely machined electrode material to obtain an octagonal radio frequency quadrupole cavity electrode.

[0051] In some embodiments, the target positioning surface and the target welding surface are the final state of the surfaces on the electrode used to achieve assembly positioning and vacuum sealing welding after final finishing.

[0052] Multiple finely machined electrode materials can be left to stand in a constant temperature environment for a preset time (e.g., 24 hours). After this period, the quality of these materials is inspected to confirm the stability and compliance of the target modulation line and target positioning surface data. Pre-assembly is then performed: for example, in the case of two horizontal and two vertical electrode materials, these materials can be precisely assembled onto a simulation base using their target positioning surfaces. Precision gauges are used to measure the gap between adjacent electrode tips, ensuring uniform gaps across the entire circumference and control within minimal tolerances. After successful pre-assembly verification, the electrodes are removed and rigorously cleaned to remove oil and oxides. Following cleaning, solder sheets are pre-placed in the solder bath on the target welding surface. Jackets, tuner port flanges, coupler port flanges, vacuum extraction flanges, etc., are then assembled, and hydrogen furnace welding is performed using welding fixtures and fixing plates. The solder melts at high temperature and fills the gaps between the welding surfaces through capillary action. After cooling, it forms a strong, dense, and highly conductive weld, ultimately combining four independent electrode materials into a complete octagonal radio frequency quadrupole field cavity electrode.

[0053] The method in this embodiment adopts a main welding surface, an auxiliary welding surface, water hole welding, and a connecting jacket, all of which are welded in one furnace, reducing the number of welding operations and lowering welding costs. Since the connecting jacket adopts a welding process, the connection between each segment and the segment cavity is more stable. Moreover, the pin hole positioning between segments can be achieved by machining pin holes on the stainless steel jacket after welding, ensuring the stability of repeated pin hole positioning.

[0054] It should be understood that the specific order or hierarchy of steps in the disclosed process is an example of an exemplary method. Based on design preferences, it should be understood that the specific order or hierarchy of steps in the process may be rearranged without departing from the scope of this disclosure. The appended method claims provide elements of various steps in an exemplary order and are not intended to limit the scope to a specific order or hierarchy.

[0055] It should also be noted that the directional terms mentioned in the embodiments, such as "up," "down," "front," "back," "left," and "right," are only for reference to the directions in the accompanying drawings and are not intended to limit the scope of protection of this disclosure. Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or constructions will be omitted when they may cause confusion in understanding this disclosure. Furthermore, the shapes, sizes, and positional relationships of the components in the drawings do not reflect their actual size, scale, or actual positional relationships.

[0056] In the detailed description above, various features are combined together in a single embodiment to simplify this disclosure. This approach to disclosure should not be construed as reflecting an intention that embodiments of the claimed subject matter require more features than are explicitly stated in each claim. Rather, as reflected in the appended claims, this disclosure is in a state of having fewer features than all of the features of the single disclosed embodiment. Therefore, the appended claims are hereby explicitly incorporated into the detailed description, with each claim representing a separate preferred embodiment of this disclosure.

[0057] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified. The term "comprising" as used in the specification or claims is interpreted in a manner similar to the term "including," as "including" is used as a conjunction in the claims. The use of any term "or" in the specification or claims is intended to mean "non-exclusive or."

[0058] The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of this disclosure. It should be understood that the above descriptions are merely specific embodiments of this disclosure and are not intended to limit this disclosure. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this disclosure should be included within the protection scope of this disclosure.

Claims

1. A method for fabricating an octagonal radio frequency quadrupole field cavity electrode, characterized in that, include: Multiple electrode materials are obtained and pre-processed to form a rough reference surface on each of the multiple electrode materials; Based on the rough reference surface of each electrode material, a finishing process is performed on one side of each electrode material to determine the initial positioning surface of each electrode material; The initial modulation line of each electrode material is determined based on the initial positioning surface of each electrode material; The actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material is determined, and each electrode material is finely processed according to the actual positional relationship to obtain multiple finely processed electrode materials; Based on the plurality of finished electrode materials, determine the target positioning surface and target welding surface of each finished electrode material; The target modulation line of each finely machined electrode material is determined according to the target positioning surface, and the multiple finely machined electrode materials are welded according to the target modulation line and target welding surface of each finely machined electrode material to obtain the octagonal radio frequency quadrupole cavity electrode.

2. The method according to claim 1, characterized in that, The plurality of electrode materials include: horizontal electrode materials and vertical electrode materials, wherein the horizontal electrode materials are W-shaped electrode materials and the vertical electrode materials are T-shaped electrode materials.

3. The method according to claim 2, characterized in that, The step of finishing one side of each electrode material based on the rough reference surface of each electrode material includes: The horizontal electrode material is placed on a prefabricated machining fixture, which includes a support block and a clamping screw. The support block is adjusted by the tightening screw to fix the horizontal electrode material; The horizontal electrode material is then precision-machined on one side after it has been fixed.

4. The method according to claim 1, characterized in that, Before finishing one side of each electrode material based on a rough reference surface of each electrode material, the method further includes: Each electrode material is subjected to stress-relief annealing.

5. The method according to claim 4, characterized in that, The stress-relief annealing treatment for each electrode material includes: The electrode material was heated for 4 hours and then kept at that temperature for 2 hours in an environment of 300℃-350℃. The electrode material, after being kept at a high temperature for 2 hours, was cooled to 60°C and then air-cooled.

6. The method according to claim 1, characterized in that, Determining the actual positional relationship between the initial modulation line of each electrode material and the initial positioning surface of each electrode material includes: Determine the dimensional and positional tolerances between the initial modulation line of each electrode material and the initial positioning surface of each electrode material; The thermal deformation law of the electrode material is determined based on the dimensional position tolerances. The actual positional relationship is determined based on the aforementioned thermal deformation law.

7. The method according to claim 1, characterized in that, A solder groove is provided on the target welding surface of the electrode material, and the welding of the plurality of electrode materials includes: Solder is filled into the solder groove of each electrode material; The plurality of electrode materials are welded according to the target modulation line, target welding surface and solder bath of each electrode material.

8. The method according to claim 1, characterized in that, Before welding the plurality of finely machined electrode materials, the method further includes: The multiple finely processed electrode materials are left to stand in a constant temperature environment for a preset time; Quality inspection was performed on multiple finely processed electrode materials after they had been left to stand for a preset time.

9. The method according to claim 1, characterized in that, Before welding the plurality of finely machined electrode materials, the method further includes: Each of the plurality of finely processed electrode materials is sequentially subjected to chemical cleaning, water rinsing, and alcohol dehydration.

10. The method according to claim 1, characterized in that, The pretreatment of the plurality of electrode materials includes: Remove the original oxide layer and stress layer from the surface of the plurality of electrode materials.

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